Some rod-less cylinders are designed so that a transfer body moves along the cylinder with the movement of a piston in the cylinder, and are equipped with a braking apparatus in order to brake and stop the transfer body at a predetermined position.
The structure of such a braking apparatus for cylinder is disclosed in, for example, Japanese Unexamined Patent Publication No. 63-176804. In this apparatus, a brake rod is rotatably supported outside the cylinder body, and extends in parallel to the moving direction of the piston. Means for rotating the brake rod is provided at one end of the cylinder body. An eccentric cam is rotatably supported on the transfer body, with its outer periphery in contact with a needle bearing or the like. This eccentric cam is provided with a cam hole to allow the brake rod to be inserted slidably, but only along the axial direction.
When the brake rod is rotated by a brake-rod rocking means, the eccentric cam rotates eccentrically. This causes a wedge effect between the eccentric cam and the needle bearing or the like, so that the cam hole of the eccentric cam is pressed against the brake rod, by the force acting in a direction orthogonal to the axial direction, thus braking and stopping the transfer body at a predetermined position.
This conventional apparatus, however, requires that a support mechanism for rotatably supporting both ends of the brake rod should be provided outside the cylinder body. This enlarges the apparatus as a whole, and complicates its structure.
In addition, the apparatus is designed so that the eccentric cam rotates by the rotation of the brake rod, to apply braking. Therefore, the traveling stroke of the transfer body is restricted by the torsional rigidity of the brake rod. Further, the torsional amount of the brake rod varies with a change in the position of the moved transfer body, so that the braking force varies accordingly.
It is therefore an object of the present invention to provide a braking apparatus for a cylinder, which can simplify its structure to downsize the apparatus as a whole.
It is another object of the present invention to provide a braking apparatus for cylinder, which can secure a large traveling stroke for a transfer body, and which can always stop the transfer body with constant braking force, regardless of a change in the position of the transfer body.